Delivering laser energy

ABSTRACT

A method for conducting laser energy to a site includes steps of bringing the proximal end of a flexible tube near the site, filling at least a proximal portion of the tube with a liquid by introducing the liquid into the tube, allowing a portion of the liquid to flow out from the proximal end of the tube toward the site, and directing laser energy from a laser energy source into the distal end of the tube, whereby a portion of the laser energy emerges from the proximal end of the tube at the site. Also, such a method in which the liquid is a radiographic contrast medium. Also, such a method for removing an obstruction from a blood vessel in an animal. Also, apparatus for delivering laser energy to a site includes a flexible tube, a liquid, the tube having an opening in a first end through which the liquid can pass, means for providing a flow of the liquid into the tube, and a source of laser energy operationally associated with a second end of the tube, wherein the tube and the liquid are adapted to cooperate, when the tube contains the liquid, to conduct laser energy from the source and to emit a portion of the laser energy from the first end of the liquid-containing tube.

BACKGROUND OF THE INVENTION

This invention relates to conducting laser energy from a laser energysource along a course that includes curves of small radius.

In many circumstances in various industrial and medical applications,matter to be cut or welded or otherwise altered or removed is located ata site that is inaccessible or difficult to reach.

Many sites within the body of an animal such as a human patient aredifficult to reach for performing surgery, because they are surroundedby hard tissues such as bone or because they are surrounded by delicatetissues which can be damaged. Sites within the thorax, such as the heartand the blood vessels near it, for example, are enclosed by bonestructures, and sites within the cranium, such as arteries supplying thebrain, for example, are surrounded by delicate brain tissue as well asby bone. The coronary arteries and the arteries of the brain can becomeoccluded for example by atheromatous plaque formations or by thrombi oremboli, with serious consequences for the patient.

One approach to providing a supply of blood to the heart when a coronaryartery is occluded is bypass surgery, that is, coronary artery bypass.The patient's thorax is opened, and a substitute conduit for supplyingblood to the heart is provided by engrafting a substitute vessel betweena point upstream from the occlusion, such as the aorta, and a point inthe coronary artery downstream from the occlusion. Coronary bypasssurgery is an involved and delicate procedure, entailing significantrisk and expense to the patient. Many patients are unable to benefitfrom bypass surgery.

In an alternative approach to relieving an occlusion of an artery, drugsare administered to cause the vessels to dilate. Not all patients canuse such drugs, however, and the results are generally only temporary,as the occluding process can continue, eventually blocking even thedilated vessel.

In still other approaches, generally termed percutaneous translumenalangioplasty, an instrument for dilating the occluded artery isintroduced, generally by means of a catheter, through an opening in theskin and through an opening in the wall of a large artery such as thebrachial artery or the femoral artery, and passed within the arteriallumens to the site of the occlusion. In balloon angioplasty, forexample, a fine guide wire is first passed to the site of the occlusionthrough the lumens of major arteries, observed by radiography as itprogresses; then a catheter having a balloon near its tip is passed overthe wire to the site, also within the arterial lumens; and finally theballoon is inflated at the site of the occlusion to stretch the walls ofthe artery and open the lumen. The results of balloon angioplasty canalso be temporary, as the occluding process in 30-40% of patients cancontinue at the site until the vessel is again blocked. Moreover, theprocedure carries risks of perforation or acute occlusion of thearteries by the instrument, and the flow of blood through the vesselbeing treated is interrupted for a time during the procedure. Onlyselected patients can benefit from balloon angioplasty, leaving manypatients with no viable treatment, including patients having atheromasinvolving long segments of vessels, or having diffuse distal arterydisease, or having arteries too tortuous to permit passage ofguidewires.

In a variety of industrial and medical applications, useful results canbe obtained by directing laser energy at a site. For example, variousmaterials melt or vaporize upon absorption of laser energy, and partsconstructed of such materials can in effect be cut or welded to achievea desired result. Laser energy can be used in surgery for alteration orremoval of tissues or obstructions or deposits by directing the energyat the matter to be altered or removed.

In a surgical technique known as laser angioplasty, conventional lightguides using fiber optics have been employed for directing laser energyonto arterial plaque formations to ablate the plaque and remove theocclusion. Individual optically conducting fibers are typically made offused silica or quartz, and are generally fairly inflexible unless theyare very thin. A thin fiber flexible enough to pass through a coursehaving curves of small radius, such as through arterial lumens from thefemoral or the brachial artery to a coronary artery, typically projectsa beam of laser energy of very small effective diameter, capable ofproducing only a very small opening in the occlusion; moreover theenergy is attenuated over relatively small distances as it passes withina thin fiber. Small diameter fibers can tend to mechanically perforatevessels when directed against the vessel wall as they are passed withinthe vessel toward the site.

In order to bring a sufficient quantity of energy from the laser to theplaque, light guides proposed for use in laser angioplasty usuallyinclude a number of very thin fibers, each typically about 100 to 200microns in diameter, bundled together or bound in a tubular matrix abouta central lumen, forming a catheter. Laser energy emerging from a smallnumber of fibers bundled together in known such catheters produceslumens of suboptimal diameter which can require subsequent enlargementby, for example, balloon dilation. Such devices do not remove anadequate quantity of matter from the lesion, and their uses aregenerally limited to providing access for subsequent conventionalballoon angioplasty.

Moreover, although individual fibers of such small dimensions areflexible enough to negotiate curves of fairly small radius, a bundle ofeven a few such fibers is much less flexible, and use of laserangioplasty has as a practical matter been limited to the larger,straighter blood vessels such as, for example, the large arteries of theleg, in which the laser energy is conducted by the light guide over onlyrelatively short distances on a relatively straight course. Couplingmechanisms for directing laser energy from the source into theindividual fibers in a light guide made up of multiple small fibers canbe complex, including lenses and mechanisms by which the individualfibers can be addressed serially by the source beam. Improper launch ofthe laser energy into such a light guide can destroy the fibers, ruiningthe instrument and endangering the patient.

More flexible light guides can be provided by filling a flexible tubewith a liquid material whose refractive index is less than that of thetube wall material. H. F. Eastgate, U.S. Pat. No. 4,045,119, describes aliquid core light guide, having a plug at each end of the tube to sealthe liquid in, for transmitting laser energy at high power from a lasersource such as a pulsed laser to an area of application.

The presence of blood near the distal end of such instruments canprevent laser light from reaching its appropriate target, such as forexample arterial plaque or a blood clot. Moreover, absorption of laserenergy by blood or blood components can result in generation of heat orformation of detonations, which can damage adjacent vessel walls.

SUMMARY OF THE INVENTION

We have discovered that laser energy can be efficiently conducted alonga course that includes curves of small radius and directed onto a targetat a remote site by launching laser energy into a liquid-filled flexibletube that is at least partially open at the end nearest the site (i.e.,the distal end of the tube) so as to permit a portion of the liquid toflow out from that end toward the target.

In general, in one aspect, the invention features a method forconducting laser energy to a site, including the steps of bringing thedistal end of a flexible tube near the site, filling the tube with aliquid that can include a radiographic contrast medium, and directinglaser energy from a laser energy source into the proximal end of thetube, whereby a portion of the laser energy emerges from the distal endof the tube at the site. In some embodiments the tube is provided withmeans for limiting the flow liquid out from the tube at the distal end.

In another aspect, the invention features a method for conducting laserenergy to a site, such as into a site of the body of an animal,including the steps of bringing the distal end of a flexible tube nearthe site, providing a flow of a liquid into the tube, and directinglaser energy from a laser energy source into the proximal end of thetube, whereby a portion of the laser energy emerges from the distal endof the tube at the site.

In preferred embodiments, a portion of the liquid is permitted to flowout from the distal end of the tube toward the site; the step ofbringing the distal end of the tube near the site includes passing itinto the body of the animal by way of an opening in the animal, or bydirect surgical approach, and includes passing it through the lumen of apassage within the body of the animal, such as through the lumen of ablood vessel of the animal. The site includes a mineral deposit, anatheromatous plaque, an atheroembolus, a thrombus, or a blood clot; thesite is located in a body space such as in an artery, in a vein, in aureter, in a common bile duct, in the trachea, in a bronchus, or in thegastrointestinal tract. The step of providing a flow of a liquid intothe tube includes passing the liquid from a source of into the tube byway of a port in the tube wall; the method further includes the step ofcontinuing to pass the liquid into the tube after the tube has beenfilled with the liquid, whereby a portion of the liquid passes out fromthe distal end of the tube.

Causing the liquid to flow from a source of liquid in a controlledmanner through the tube and distally out from the tube during thetreatment can produce a column of liquid between the distal end of thetube and the target, effectively permitting a continuous guide for thelaser energy for a short distance beyond the distal end of the tube. Avariety of body fluids, such as, for example, blood or urine, haveindices of refraction sufficiently low with respect to the liquid in thetube to provide such a light guide effect beyond the distal end of thetube. Moreover, matter that may interfere with the laser treatment,including substances normally present at the site, such as blood in thecase where the site is within a blood vessel, or substances produced atthe site as debris during the treatment, can be continually flushed awaywithout interrupting the procedure by the flow of liquid out from thedistal end of the tube.

In another aspect, the invention features a method for removing anobstruction from a blood vessel in an animal, comprising bringing thedistal end of a flexible tube near the obstruction, filling the tubewith a liquid by passing the liquid into the tube, continuing to passthe liquid into the tube after the tube has been filled with liquid, sothat a portion of the liquid passes out from the tube at the distal end,and directing laser energy from a source into the proximal end of thetube, whereby a portion of the laser energy emerges from the proximalend of the tube and strikes the obstruction. Where the obstructionincludes an atheromatous plaque, the method can be one for treatingatherosclerosis; where the obstruction includes a thrombus, the methodcan be one for treating thrombosis or thromboembolism.

The method does not require completely restricting the flow of bloodthrough the vessel being treated, so the procedure can be carried outwithout haste. Moreover, the flushing action of the liquid flowing outfrom the tube toward the target can enhance laser energy delivery byremoving blood, which can absorb wavelengths of laser energy that can beuseful for removal of plaque or thrombus.

In another aspect, the invention features apparatus for delivering laserenergy to a site, including a liquid, a flexible tube having an openingin one end, arranged and adapted to be brought near the site, throughwhich the liquid can pass, means for providing a flow of the liquid intothe tube, and a source of laser energy operationally associated withanother end of the tube, wherein the tube and the liquid containedwithin it can cooperate to conduct laser energy from the source and toemit a portion of the laser energy from the second end of the tube.

In preferred embodiments, at least a portion of the tube is adapted tobe bent without substantial change in cross-sectional shape or withoutkinking into a curve having a radius of curvature as small as 20 mm,more preferably as small as 10 mm; The tube includes a wall having arefractive index n_(w), one surface of the wall describing the lumenalsurface of the tube, and the liquid has a refractive index n_(f),wherein n_(f) is greater than n_(w) ; the values of n_(f) and n_(w) aresuch that the ratio

    r.sub.f,w =(n.sub.f)/(n.sub.w)

is greater than 1.0, more preferably greater than about 1.05, still morepreferably greater than about 1.1; the value of n_(f) is about 1.46, orat least about 1.46; the value of n_(w) is about 1.33, or at least about1.33; the liquid includes a radiographic contrast medium; the liquid isbiocompatible; a support layer surrounds the wall; the wall is made of apolymer, preferably a fluorinated polymer, such as tetrefluoroethylenehexafluoropropylene (FEP) or polypentadecafluorooctylacrylate elastomer.A cap is affixed to the first end of the tube; the cap is arranged andadapted to substantially restrict movement of the liquid out from thetube by way of the first end; the cap is configured to provide a smoothand rounded proximal surface; the cap has a bore through itsubstantially aligned with the axis of the tube, preferably of adiameter sufficiently to permit passage of a guidewire through it,preferably sufficiently small to restrict the flow of the liquid throughit, preferably about 500 micrometers, or at least about 500 micrometers;the cap is made of quartz, or of sapphire; the cap has a reflectivesurface arranged and adapted to direct the laser energy in a directionaway from the axis of the tube; The lumen of the tube has a transversedimension between about 1 mm and 3 mm; the lumen has a substantiallycircular cross-sectional shape; it has a diameter between about 1 mm and3 mm. The apparatus further includes a coupler at a the second end ofthe tube for conducting energy from the source of laser energy to theliquid-containing tube; the coupler comprises a window, a lens, or anoptical fiber (preferably inserted into the lumen of the tube); thecoupler is made of quartz or fused silica; the means for providing aflow of the liquid into the tube includes a conduit for conducting theliquid between the source and the tube; the tube includes a portintermediate its first and second ends for passing the liquid betweenthe source and the tube; the means for providing a flow of the liquidinto the tube further includes a filter to prevent bubbles from movinginto the tube.

In other embodiments, the tube wall includes a reflective layer, onesurface of which describes the lumenal surface of the wall; preferablythe reflective layer is of a reflective polymer or metallized material,such as a material including aluminum or silver, coextruded with orbonded to the lumenal surface of the tubing material.

The liquid-core light guide according to the invention can be madesufficiently flexible to negotiate the small curves commonly encounteredin finer arteries such as the coronary arteries, while projecting aneffective beam sufficiently broad to remove an occlusion. The tubing forthe light guide itself can be simply and inexpensively made by, forexample, a continuous extrusion or coextrusion process, and cut forlength as required for each particular use. Advancing the light guidethrough arterial or venous lumens can be facilitated by initiallyadvancing a guidewire along the course to be followed and then advancingthe light guide over the guidewire to the target location.Alternatively, a guiding catheter can be emplaced at the origin of theobstructed artery and the light guide can be advanced within the lumenof the guiding catheter. The laser energy source can be coupled to thelight guide in a straightforward fashion, presenting few launchcomplications. The laser energy can be launched directly from the laserthrough a focusing lens to the light guide or alternatively it can belaunched initially into a conventional fiber inserted into the lumen ofthe light guide at the proximal end.

The liquid and the tube can be made from biocompatible materials. Usinga radiographic contrast medium as a liquid permits continuousfluoroscopic imaging of progress throughout the procedure withoutinterruption. Moreover, a light guide containing a radiographic contrastmedium can be used with fluoroscopic monitoring to deliver laser energywith precision in nonmedical applications where the site to be treatedis accessible only by way of a tortuous pathway, such as, for example,in repair or reconstruction of internal parts of hydraulic apparatus inwhich the hydraulic fluid is a hazardous material.

DESCRIPTION OF THE PREFERRED EMBODIMENTS DRAWINGS

FIG. 1 is a somewhat diagrammatic view of portions of a liquid corelight guide according to the invention, partially cut away along thelong axis of the tube.

FIG. 2 is a section thru the light guide of FIG. 1 at 2--2.

FIG. 3 is a somewhat diagrammatic view of the proximal portion of aliquid core light guide, cut away along the long axis of the tube,showing a liquid port and conduit for passing liquid into the tube.

FIGS. 4 through 7 and 9 are somewhat diagrammatic views of the distalportion of a liquid core light guide, cut away along the long axis ofthe tube, showing end caps in various configurations.

FIG. 8 is a section thru the distal portion of a liquid core light guideof FIG. 7 at 8--8.

FIG. 10 is a somewhat diagrammatic view of portions of an alternateliquid core light guide of the invention, partially cut away along thelong axis of the tube.

FIG. 11 is a section thru the light guide of FIG. 7 at 8--8.

FIG. 12 partially cut away through the long axis of the tube, showing awindow for coupling a source of laser energy to the light guide.

FIG. 13 partially cut away through the long axis of the tube, showing analternate laser coupler employing an optical fiber.

FIG. 14 is a somewhat diagrammatic view of the proximal portion of analternative liquid core light guide of the invention, cut away along thelong axis of the tube, having a reflective lumenal surface.

FIG. 15 is a somewhat diagrammatic view of the distal portion of aliquid core light guide of the invention, cut away along the long axisof the tube, in combination with a balloon dilation device.

FIG. 16 is a somewhat diagrammatic view of the distal portion of aliquid core light guide of the invention, cut away along the long axisof the tube, showing a light diffusion balloon.

STRUCTURE AND OPERATION

FIGS. 1 and 2 are views of a liquid core light guide of the invention.The light guide includes a tube, shown generally at 10, whose wall 16encloses a lumen 24 which is filled with a liquid 26. The inner surfaceof wall 16 defines lumenal surface 22 of tube 10.

Laser energy can be directed from a source of laser energy (not shown inFIGS. 1 and 2) into proximal end 14 of liquid filled tube 10, asindicated generally by arrow I. The energy passes within the liquidfilled tube toward distal end 12. The energy is attenuated as it passesaway from the source, so that a portion of it emerges from distal end12, as indicated generally by arrow O. The proportion of the energyintroduced to the proximal end that emerges from the distal end of theliquid-filled light guide depends upon the dimensions and physicalcharacteristics of the liquid and the tube wall, and on the extent towhich the tube follows a curving course.

Referring now to FIG. 3, port 62 through wall 16 is provided nearproximal tube end 14, and one end of conduit 64 is coupled to point 62.Fluid can be introduced at the other end of conduit 64 as indicated byarrow F from a source of liquid such as a syringe or a pump, such as,for example, a peristaltic pump (not shown in FIG. 3), into tube 10through conduit 64 via port 62. Similarly a conventional guide wire (notshown in FIG. 3) can be introduced into tube 10 through conduit 14 viaport 62.

The materials for wall 16 and for liquid 26 are selected in part toprovide a high degree of internal reflection at the lumenal surface;that is, wall 16 and liquid 26 are each transparent to the laser energyto be conducted through the light guide, and the index of refractionn_(w) of wall 16 is greater than the index of refraction n_(f) of liquid26.

Further, the material for wall 16 is selected in part to providestructural strength as well as flexibility so that the liquid-filledlight guide can be bent through curves of small radius without kinkingor substantially distorting the cross-sectional geometry of the tube.

Preferably wall 16 is made of a fluorinated ethylenepropylene, such asis available commercially for example as "FEP Teflon®", and the liquidis a radiographic contrast medium, such as is available commercially forexample as "Renographin 76®". FEP Teflon® has a refractive index about1.33, and Renographin 76® has a refractive index about 1.46; the ratioof their refractive indices is thus about 1.1, providing forsubstantially total internal reflection even at fairly steep angles ofincidence. Preferably the lumenal surface of the tube is smooth, asirregularities in the surface can introduce unsatisfactoryirregularities in angles of incidence. Preferably the tube has acircular cross-sectional shape, and the inner diameter (i.e. thediameter of the lumen of the tube) is about 1-3 mm according to thediameter of the arterial lumen to be opened. Preferably the thickness ofthe wall 16 is at least about two times the wavelength of thetransmitted light. Such a tube, 110 cm long, with a wall of FEP Teflon®and containing Renographin 76®, can transmit from the distal end about60% of laser energy at 480 nm, launched through a refractiveindex-matched lens or window into the distal end from a laser.

Alternatively, the laser energy can be launched into a conventionalquartz fiber from the laser, and the quartz fiber can be inserted intothe proximal end of the tube. However, proximal portions of the tubewhich contain such a fiber are thereby rendered much less flexible, andit is advantageous in applications where great flexibility is requiredparticularly in a distal portion of the light guide not to insert thefiber so far that the I; total end of the fiber reaches into thepreferably flexible distal region of the light guide.

Such a tube of such composition can have a "memory"; that is, the tubecan be preformed to conform to a particular desired curvature, so that,while it can be straightened or flexed, it will tend to conform to aparticular anatomical course corresponding to the preform curvature.

Some materials that are optically suitable for use as a tube wall arestructurally unsuitable or less suitable; that is, they areinsufficiently flexible, or they collapse or kink or otherwise aredistorted when they are bent through curves of small radius. FIGS. 10and 11 show an alternate construction for the tube, in which the tube 16includes inner wall layer 18, whose inner surface defines the lumenalsurface 22 of the tube wall 16, and outer supportive layer 20. Innerwall layer 18, situated adjacent the lumen 24 of tube 10, is constructedof material having suitable optical characteristics, as described abovewith reference to FIGS. 1 and 2. Outer wall layer 20, which can bebonded to inner wall layer 18 or coextruded with it, is formed ofmaterial having suitable mechanical properties, so that tube wall 16 hasstructural strength as well as flexibility, as described above generallywith reference to FIGS. 1 and 2.

The laser light guide operates generally as follows, with specificreference to its use for ablating arterial plaque occluding a coronaryartery. Tube 10 is filled with liquid 26, and a source of laser energyis coupled to the distal end 14 of the liquid-filled tube. Fluid-filledtube 17 is introduced proximal end first through an opening in the skinand through the wall of a large artery such as the femoral artery, andis then passed translumenally toward the site of the occlusion to betreated by laser energy, until the distal end resides in the lumen ofthe occluded artery and is directed toward the occlusion. If the liquidis a radiographic contrast medium such as Renographin 76®, the progressof the tube toward the site can be followed by x-ray withoutinterruption either with or without use of a guide wire. Once theproximal tip has reached the site and is directed toward the target, afurther quantity of liquid can be introduced into the tube from a liquidsource, causing some liquid to emerge (i.e. flow) from the proximal endof the tube toward the target. Blood situated between the tube and thetarget can interfere with laser ablation of the plaque, because theblood absorbs nearly all wavelengths of laser energy better than doesplaque. The liquid passing from the distal end of the tube displacesblood between the tube and the target removing this interference. As theemerging liquid displaces the blood, it provides a liquid channelproximal to the proximal end of the tube for passage of laser energy tothe target. Moreover, the index of refraction of blood is about 1.34,sufficiently low relative to that of the liquid that the bloodsurrounding the liquid in this channel forms an effective light guidebetween the distal end of the tube and the target. Such a temporaryliquid-core, liquid-clad light channel can be effective over distancesin the order of about a centimeter for time intervals generallysufficient in the usual circumstance to complete the ablation and openthe arterial lumen.

Then the laser energy source is activated to produce laser energy havingthe desired wavelength and pulse duration and intervals. The progess ofthe laser ablation of the target can be observed by x-ray, as the liquidserves not only as a light guide component but also as a radiologiccontrast medium. When the ablation has been completed, the liquid-filledtube is withdrawn.

A guide wire can be used in the above-described procedure as desired,for example, if the walls of the arteries to be traversed by the tubethemselves contain plaque formations that would interfere with thepassage of the proximal end of the tube during insertion. The guide wiretraverses the liquid-filled lumen of the tube. A preformed tube asdescribed above follows the course of the guide wire during insertion;once the tube is emplaced the guide wire can be removed, and the tubethen conforms to its curving course through the arteries.

Alternatively, as shown in FIGS. 4 through 9, the distal end of the tubecan be provided with an end cap, to inhibit flow of liquid out from thedistal end. With reference to FIG. 4, end cap 40 has generallycylindrical portion 44 whose diameter is such that portion 44 can bepress fitted into tube 10; and an end portion 45 forming a shelf 46 thatabuts proximal tube end 12. A hole 52 runs through the center of end cap40, situated so that it is aligned with the long axis of tube 10 whenend cap 40 is in place. Hole 52 has a diameter sufficiently large topermit passage of a guide wire. Where desired hole 52 can be made with adiameter sufficiently small that the flow of the liquid out from thedistal end of the tube is restricted under conditions of use. Forstandard guide wires, and for aqueous liquids, a diameter about 500microns can be suitable. End portion 45 is shaped to provide a smoothand rounded distal surface, so that the light guide can be easily passeddistally to the site without becoming caught or damaging the vesselwall.

FIGS. 5 and 6 show alternative end caps 50 and 60, adapted to be moresecurely fastened to the distal end of tube 10. Generally cylindricalprotion 54 of end cap 50 includes annular ridge 58, and tube 10 isprovided near end 12 with annular groove 59 into which annular ridge 58fits when end cap 50 is seated with shelf 56 of end portion 55 inabutment with tube end 12. Generally, cylindrical portion 64 of end cap60 includes annular groove 68. End cap 60 is press fitted into tube 10so that shelf 66 of end portion 66 abuts tube end 12, and then retainingring 70 is placed about tube 10, compressing an annular portion of wall16 into groove 68. End caps 50 and 60 are provided with holes 52 and 62corresponding to hole 42 in end cap 40 as described above with referenceto FIG. 4.

FIGS. 7 and 8 show an alternate embodiment of a liquid core light guideof the invention, in which a passage for the guide wire is providedseparate from the lumen containing the laser energy conducting liquid.Tube wall 16 is provided with a lumen 24 bounded by lumenal surface 22similar to that described above with reference to FIGS. 1 through 3, 10and 11, in which the liquid is located. A thickened portion 90 of wall16 is provided with a longitudinal bore 92 through which a guide wirecan pass. End cap 80 having a generally cylindrical portion 84 is pressfitted or heat welded into the proximal end 88 of the tube. Generallycylindrical portion 84 of cap 80 is provided with an annular swelling86, which conforms to the inner surface of the tube wall to form asecure attachment when the cap is assembled into the tube. End cap 80can be provided with generally axially situated hole 82, if it isdesired to permit a flow of liquid out from the proximal end of thetube. Alternatively, if no hole is provided in end cap 80, then end cap80 provides a seal for preventing a flow of the liquid out from thetube, as may be desired for example if the liquid is corrosive to thesurroundings near the site to be treated by the laser energy; or if theliquid is toxic or otherwise not biocompatible, as may be a concern in amedical application. Many liquids that are suitable for UV or for IRlaser transmission, as generated for example by excimer, Holmium, orErbium YAG lasers, are toxic or nonbiocompatible, while manyradiographic contrast media transmit UV or far IR wavelengths onlypoorly.

FIG. 9 shows an alternative construction for the cap, whereby the capprovides a reflective surface to direct the laser energy out through thetube wall in a direction away from the axis of the tube. End cap 120 isaffixed generally as described above into the distal end of the tube.The proximal end of generally cylindrical portion 124 of cap 120 isprovided with a reflective surface 126, which is shaped and oriented sothat it reflects the laser energy in a desired direction, such as forexample a direction generally perpendicular to the tube axis, as shownat arrows R in FIG. 9. A side hole 128 can be provided in wall 16 in thearea where the light reflected from reflective surface 126 as at arrowsR passes through the wall, to allow fluid to pass out from the tubetoward a site situated lateral to the tube. This flow of fluid displacesblood in the zone between the tube wall and the target site, providing atemporary liquid-core, liquid-clad light guide as described above forconducting the laser energy to the target.

Alternatively, a window can be affixed within hole 128 of wall 16, madeof, for example, quartz or sapphire, which is transparent to thereflected light but does not allow passage of the liquid. Such a windowcan prevent leakage of the liquid into the site, and can be desirablewhere, for example, the liquid is itself toxic or otherwisenonbiocompatible; or, in industrial applications, where the liquid isincompatible with the materials at the site.

As desired, the reflective surface 126 can be planar, or can be curvedsuch that it causes the reflected laser energy to diverge or converge.

The end cap can be formed for example of quartz or of fused silica byfor example end-melting a length of quartz or fused silica capillarytube having appropriate dimensions. The cap material can be opticallymatched with the liquid, such that, for example, the liquid and the caphave nearly the same index of refraction, and the interface between theliquid and the cap is not seen by the passing laser energy. If a cap isprovided with a reflective surface, for example as described above withreference to FIG. 9, then the cap can have an index of refractionsufficiently different from that of the liquid to provide reflection atthe interface, or the reflective surface can be provided with areflective film or coating.

The light guide can be coupled to the source of laser energy by meansknown in the art of laser light guides. FIG. 12 shows a window 98affixed to the distal end 14 of the tube. The laser energy is directedas shown generally by arrow I in a direction generally coaxial with thetube lumen 24 from a laser energy source, a portion of which isindicated diagrammatically at L, toward window 98, through which itpasses into the tube lumen 24. Such a window can be made for example ofquartz or fused silica having an index of refraction matched with thatof the liquid, so that the interface between the liquid and the windowis not seen by the passing laser energy.

An alternative coupler is shown in FIG. 13. This coupler can be used tolaunch the laser energy into the light guide from a conventional opticalfiber that is conventionally coupled to the source of laser energy, andthe coupler provides a Y connector shown generally at 100 through whichthe liquid can be introduced while the light guide is in use. Yconnector 100 includes a generally cylindrical barrel 102 having an end103 configured to fit over the distal end 14 of the tube. A seal isestablished between barrel 102 and tube end 14 by heat-shrinking alength of tubing material 105 over the joint. Conduit 104 projects frombarrel 102, to provide for introduction of liquid from a source ofliquid, indicated diagramatically at S, into coupler 100 and lumen 24 ofthe tube. A conventional bubble filter, indicated generally at B, isinterposed across the flow of liquid, indicated generally at F, forpreventing introduction of gas bubbles into the lumen 24 of the tube.Proximal end 108 of coupler 100 is affixed with a cap 106, which isprovided with bore 107 through which conventional optical fiber 114 canpass. Proximal cap 106 is provided with annular groove 110, whichaccommodates O-ring 112 to provide a seal between proximal cap 106 andfiber 114. Fiber 114, which can be provided with a conventional ball tip116, is advanced proximally into lumen 24 of the tube as far as isdesired. Because fiber 114 is insufficiently flexible to pass through acourse having curves of small radius, fiber 114 should not be advanceddistally beyond portions of the tube where such bends are not likely tobe encountered. Preferably, ball tip 116 is advanced only as far as apoint outside the body into which the light guide is to be passed, sothat the launch point between the fiber tip and the liquid can beinspected through the tube wall while the light guide is in use.

Where the optical fiber has a diameter between about 300 and 600 μ, andthe lumenal diameter of the tube is greater, as for example about 1-3mm, liquid can flow as indicated generally by arrows F within the tubeabout the fiber while it is being introduced and once it is in place.The inserted fiber confers increased rigidity upon the tube, leaving adistal portion of the tube, into which the fiber does not reach,flexible; in many applications, such as, for example, laser irradiationof a coronary artery, this distal portion of the tube is the portionrequiring the greatest flexibility.

Preferably the fiber is inserted so that its tip rests in a relativelystraight portion of the tube, and with the fiber placed as nearlycoaxially as possible to provide launch of the energy from the fiber tipas nearly coaxially with the tube as possible. A centering device at thetip of the fiber can help to maintain the coaxial relationship; and afiber made, for example, of a quartz having a low index of refractioncan be used to help direct the light principally in a longitudinaldirection at the point of launch (i.e. the point at which the laserenergy passes out of the distal end of the fiber 114 and into the liquidwithin the distal portion of the lumen 124).

In an alternative embodiment, shown in FIG. 14, the light guide includesa tube, shown generally at 110, whose wall 116 encloses a lumen 124which is filled with liquid 126. Wall 116 includes outer layer 120, andinner layer 118. Inner layer 118 has a reflective surface defininglumenal surface 122 of tube 110. Inner layer 118 can be made of ametallized materials containing, for example, aluminum or silver; orinner layer 118 can be made of a reflective polymer. Outer layer 120 isformed of material having suitable mechanical properties, so that tubewall 116 has structural strength as well as flexibility, as describedabove generally with reference to FIGS. 1 and 2 and FIGS. 10 and 11. Atube made of such materials and filled with liquid can be bent throughcurves of small radius without kinking or substantially distorting thecross-sectional geometry of the tube, and can work as a light guide fordelivery of laser energy.

In an alternative embodiment, shown in FIG. 15, apparatus is showngenerally at 210 combining a liquid filled light guide of the inventionwith a balloon catheter adapted to cooperate with the liquid lightguide. The light guide includes a tube 211 whose wall 216 has a lumenalsurface 222 surrounding a lumen 224 that can be filled with liquid 226.The wall 216 and the liquid 226 are selected as described above withreference to FIGS. 1 and 2 to have optical characteristics-such that theliquid 226 and the wall 216 together from a liquid core light guide;laser energy directed into the proximal end (not shown in FIG. 15) ofliquid filled tube 211 passes within lumenal space 224 toward distal end212 of tube 211, from which a portion of the light emerges, as indicatedgenerally by arrow O. Tube 211 is contained in generally coaxialrelation within a catheter tube 230 so that a space 234 is containedbetween catheter wall 230 and tube wall 216. Distal tube end 212 isaffixed to proximal end 232 of catheter 231 in annular sealed relationat 213. As in a conventional balloon dilation catheter, catheter wall230 includes an expandable wall portion 232, so that when fluid isintroduced under pressure into the space 234, the expandable portion 232of wall 231 swells or inflates to a configuration such as that forexample shown in FIG. 15.

Adaptation of a balloon dilation catheter and combination of it with aliquid core light tube as illustrated for example in FIG. 15 can be usedfor combination balloon/laser angioplasty as follows. The catheter, withthe balloon deflated, containing the light tube can be inserted to thesite where angioplasty is to be carried out, using a guide wire withinthe lumen of the light guide if desired. When the site to be treated,such as an atheroma, is reached, laser energy can be directed throughthe light guide onto the site to ablate a portion of the plaque to forma channel sufficient to permit passage of the catheter. Then thecatheter can be inserted through the channel to bring the exandableballoon portion into the angioplasty site, and fluid can be introducedinto the balloon to cause it to inflate and expand the blood vessel atthe site as in cenventional balloon angioplasty. Finally the balloon canbe deflated and the catheter removed.

In another embodiment, shown in FIG. 16, an area of the lumenal surfaceof a vessel wall can be treated with diffuse light directed to the sitethrough a liquid filled light guide according to the invention. In thisembodiment the light guide includes a tube 316 constructed of amaterials selected in part to provide a high degree of internalreflection at the lumenal surface 322 when tube 316 is filled with asuitable liquid, and in part to provide structural strength andflexibility so that the liquid-filled light guide can be bent throughcurves of small radius without kinking or substantially distorting thecross-sectional geometry of the tube, as described above with referenceto FIGS. 1 and 2 or FIGS. 10 and 11. Contained within tube 316 ingenerally coaxial relation is an inner tube 330 having bore 334 throughwhich a conventional guide wire can be passed. Inner tube 330 isconstructed of materials selected also in part to provide a high degreeof reflection at the outer surface 332 when tube 316 is filled with asuitable liquid 326, and in part to be strong and flexible. Affixed tothe distal end 336 of inner tube 330 is an end cap 340 having bore 342aligned with inner tube bore 334, through which a conventional guidewire can pass. End cap 340 is generally similar to end caps describedabove with reference to FIGS. 4 through 6. A generally cylindricalportion 344 of end cap 340 is affixed to a flange 346, which can beconstructed of the same material as tube 316. An expandable sleeve 350,of a material transparent to the light to be delivered to the site, isaffixed in annular sealed relation at one end 352 to the distal end 312of tube 316 and at the other end 354 to the distal end of flange 346, sothat sleeve 350 forms a transparent portion of the wall of the lighttube surrounding a space 356 distal to the tube end 312.

A conventional balloon angioplasty generally produces a dilated portionof the vessel in which the lumenal surface contains cracks and fissures.These cracks and fissures fill with blood and other matter containedwithin the vessel. Often, after a time, this matter disperses or isdislodged from the cracks and fissures, and the dilated portion of thevessel collapses, forming a restenosis at the angioplasty site. Thematter can be caused to remain in the cracks for a greater time,delaying the collapse of the vessel and the restenosis, by denaturingthe material, for example by application of heat, so that the materialforms in effect a mortar in the cracks. The matter can be heated anddenatured by, for example, irradiating the dilated vessel wall withdiffuse light energy.

A liquid filled light guide constructed according to the invention andhaving a transparent wall portion as illustrated for example in FIG. 16can be used to provide such an irradiation of the inner wall of a vesselfollowing balloon angioplasty as follows. Following balloon angioplastythe balloon catheter is withdrawn, and, while the cracks and fissuresare still filled with matter, the liquid filled light guide is inserted,over a guide wire if desired, so that the transparent portion of thewall of the light guide rests within the dilated portion of the vessel.Then further liquid is introduced under pressure through the lumen 324of the light guide, expanding the expandable transparent wall portion350 within the dilated portion of the vessel. Then light is directedthrough the lumen 324 of the light guide from the distal end (not shownin FIG. 16) toward the distal end 312, from which a portion of the lightemerges into the liquid-filled space 356, as indicated generally byarrows O. Because the light can pass outward through expandabletransparent wall portion 350, the light is not guided lengthwise in theportion of the tube surrounding liquid-filled space 356, and the lightleaks outward diffusely from the tube through transparent expanded wallportion 350, as indicated generally by arrows D. The leaking light canthen be absorbed by the lumenal portions of the vessel wall surroundingthe expanded portion 350 of the light guide, where the light candenature the matter that has collected in the cracks and fissures of theinner vessel wall, having the effect of mortaring the wall and helpingto prevent its collapse.

Other Embodiments

Other embodiments are within the following claims. For example, theliquid and the material of the inner wall of the light guide can beselected from any of a variety of materials, provided the tube wall hassuitable mechanical properties and provided the indices of refraction ofat least an inner layer of the wall and of the liquid differ relativelyso that they cooperate to provide a light guide effect. The liquid andthe inner wall material preferably are selected to maximize the ratio ofthe indices of refraction of the liquid and of the inner wall of thetube. Where the wall material has been selected, the index of refractionof the liquid must be at least as high as that of the selected wallmaterial; and, conversely, where the liquid has been selected, the indexof refraction of the inner wall material must be lower than that of theselected liquid, as discussed generally above.

Where a flow of the liquid into the milieu beyond the proximal end ofthe light guide is employed to provide a temporary liquid-core,liquid-clad light guide between the proximal end of the tube and thetarget site, the selected liquid must have an index of refractiongreater than that of the milieu. The liquid can be introduced into thetube by means, for example, of a syringe or of a pump, such as forexample a peristaltic pump, configured and arranged so that it iscapable of providing a flow of fluid without introducing air bubblesinto the tube. Preferably where the means for providing the flow offluid is capable of producing high pressures, conventional means areprovided for shutting off the flow when the pressure exceeds a level ofsafety.

Any of a variety of radiographic contrast media can be used, including anonionic contrast medium such as, for example, contrast mediacommercially available as Hexabrix® or Omnipaque®, or an ionic contrastmedium such as, for example, contrast media commercially available asRenographin 76®, or Angiovist®.

Admitting a fiber into the light guide will make much less flexible thatportion of the light guide containing the fiber; in circumstances wheregreat flexibility is needed principally in a distal portion of thecatheter, such as, for example, where the site to which the laser energyis to be delivered is in a coronary artery, the fiber can be admittedonly as far as a point proximal to the distal portion of the tube inwhich great flexibility is required. This can provide for astraightforward launch of energy into the liquid light guide, and canshorten the distance within the liquid light guide through which theenergy is transmitted, thereby reducing losses and increasing thetransmission efficiency of the delivery apparatus.

We claim:
 1. A flowing fluid laser catheter system for delivering laserenergy to target matter located within a mammalian body, said cathetercomprising:an elongate, pliable catheter body having a proximal end, adistal end and at least one lumen extending longitudinally therethrough, said lumen being defined by a luminal surface; an outletopening formed in the catheter body such that fluid flowing through saidat least one lumen may pass out of said outlet opening, a source ofliquid radiographic contrast medium which is unmixed with otheroxygen-bearing fluid and which is connected to said at least one lumenand useable to pass a flow of liquid radiographic contrast mediumthrough said lumen, out of said outlet opening and into contact withsaid target matter; a laser transmitting member which is connectable toa laser generating apparatus, said laser transmitting member beingoperative to pass laser energy from said laser generating apparatus intoradiographic contrast medium which is flowing trough said at least onelumen, such that the laser energy will be carried by said flow ofradiographic contrast medium out of said outlet opening and into contactwith said target matter.
 2. The catheter system of claim 1 wherein saidsource of radiographic contrast medium includes apparatus for infusingsaid radiographic contrast medium through said at least one lumen andout of said outlet opening with sufficient force to displace body fluidfrom the area between said outlet opening and said target matter,thereby creating a column of said radiographic contrast medium whichcarries said laser energy from said outlet opening into direct contactwith said target matter.
 3. The catheter system of claim 1 wherein thesource of liquid radiographic contrast medium comprises a source of aniodinated contrast medium.
 4. The catheter system of claim 1 wherein thesource of liquid radiographic contrast medium comprises a source of anionic contrast medium.
 5. The catheter system of claim 1 wherein thesource of liquid radiographic contrast medium comprises a source of anonionic contrast medium.
 6. The catheter system of claim 1 wherein atleast a portion of said catheter body may be bent into a curve having aradius of curvature no larger than 10 mm without changing the crosssectional shape of the catheter body at the location of said curve. 7.The catheter system of claim 1 wherein at least a portion of saidcatheter body may be bent into a curve having a radius of curvature nolarger than 20 mm without changing the cross sectional shape of thecatheter body at the location of said curve.
 8. The catheter system ofclaim 1 wherein the source of liquid radiographic contrast mediumcomprises a source of a contrast medium which has a refractive indexn_(f) and said luminal surface has a refractive index n_(w), therefractive index n_(f) of said contrast medium being greater than therefractive index n_(w) of said luminal surface.
 9. The catheter systemof claim 8 wherein the ratio of n_(f) to n_(w) is greater than 1.0. 10.The catheter system of claim 9 wherein said ratio is about 1.05.
 11. Thecatheter system of claim 9 wherein said ratio is about 1.1.
 12. Thecatheter system of claim 1 wherein said laser transmitting membercomprises an optical fiber having a proximal end which is coupleable tosaid laser generating apparatus and a distal end, said optical fiberextending through a portion of said at least one lumen such that thedistal end of said optical fiber is positioned within said at least onelumen a spaced distance proximal to said outlet opening such that laserenergy will pass from said optical fiber into the radiographic contrastmedium flowing through said lumen and said laser energy will then becarried by said flow of radiographic contrast medium through theremainder of said at least one lumen, out of said outlet opening, andinto contact with said target matter.
 13. The catheter system of claim12 further comprising fiber centering apparatus which will hold at leastthe distal end of said optical fiber in a substantially centeredposition within said at least one lumen such that a fluid flow spacesurrounds at least the distal end of said optical fiber.
 14. Thecatheter system of claim 13 wherein said source of liquid radiographiccontrast medium is connected to said catheter body at a location whichis proximal to said optical fiber supporting apparatus such thatradiographic contrast medium will flow through said fluid flow space andlaser energy may pass from the distal end of the fiber, into said flowof radiographic contrast medium and will be carried by said contrastmedium out of said outlet opening and into contact with said targetmatter.
 15. The catheter system of claim 14 wherein the distal end ofsaid optical fiber is aligned with said outlet opening.